JP2014504897A - Tension control in the operation of multi-joint medical devices - Google Patents

Abstract

Control systems and methods for medical instruments use measurements to determine and control the tension that an actuator applies through the instrument transmission system. The use of tension and feedback allows control of a medical device having a transmission system that provides non-negligible compliance between the joint and the actuator even when the joint position cannot be directly related to the actuator position. One embodiment determines joint torque and tension from the difference between the desired and measured joint positions. Other embodiments determine joint torque and tension from the desired and measured position of the instrument tip. The determination of tension from the joint torque can be performed using joint sequential evaluation in order from the distal end of the instrument to the proximal end of the instrument.

Description

  Minimally invasive medical procedures often use instruments that are controlled using a computer or via a computer interface. For example, FIG. 1 shows a robot controlled instrument 100 having a simplified structure to illustrate the basic operating principles of current robot controlled medical instruments. (As used herein, the terms “robot” or “robot” and the like include a remote control or remote control robot aspect.) The instrument 100 is an elongated shaft or distal end of a main tube 120. Includes a tool or end effector 110. In the illustrated example, the end effector 110 is a jawed tool such as forceps or scissors with independent jaws 112 and 114, at least the jaw 112 being movable to open and close relative to the jaw 114. is there. In use during a medical procedure, the end effector 110 at the distal end of the main tube 120 can be inserted through a small incision in the patient and positioned at a work site within the patient. The jaw 112 can then be opened and closed, for example, during the performance of a surgical operation, so it must be precisely controlled to perform only the desired movement. Practical medical instruments generally require a lot of freedom of movement in addition to opening and closing the jaws 112 and 114 to perform medical procedures.

  The proximal end of the main tube 120 attaches to a transmission or drive mechanism 130, sometimes referred to as a back end mechanism 130. The tendons 122 and 124, which may be stranded wires, rods, tubes, or a combination of these structures, extend from the back end mechanism 130 through the main tube 120 and attach to the end effector 110. A typical surgical instrument also provides the back end mechanism 130 with the end effector 110, such that the back end mechanism 130 can manipulate the tendon to actuate the end effector 110 and / or other driven elements of the instrument 100. Also included is a wrist mechanism (not shown) or an additional tendon (not shown) that connects to the driven vertebrae of the main tube 120. FIG. 1 shows a jaw 112 having a pin joint structure 116 that provides one degree of freedom movement of the jaw 112. Two tendons 122 and 124 are attached to the jaw 112 and the pulley 132 of the back-end mechanism 130 such that rotation of the pulley 132 causes the jaw 112 to rotate.

  The pulley 132 is attached to a drive motor 140, which can be at the end of a mechanical arm (not shown), and the control system 150 electrically controls the drive motor 140. The control system 150 typically includes a computer system with appropriate software, firmware, and peripheral hardware. Among other functions, the control system 150 typically provides a surgeon or other system operator with an image (eg, a stereoscopic view) of the work site and the end effector 110, and the surgeon controls the movement of the end effector 110. A control device or manipulator that can be operated as described above is provided. The software or firmware required to interpret the user's operation of the controller and generate motor signals to cause the corresponding movement of the jaw 112 is generally complex in real robot medical instruments. Considering some of the control tasks, the generation of control signals for the drive motor 140 is typically a relationship between the angle or position of the jaw 112 and the angle or position of the drive motor 140 or pulley 132 of the backend mechanism 130. Is used. If the tendons 122 and 124 are rigid (eg, if tendon extension is negligible), the control system 150 may determine the instrument 100 to determine the control signals needed to move the jaw 112 as directed by the surgeon. A direct relationship between the angular position of the drive motor 140 and the angular position of the jaw 112 can be used as determined by the geometry. For example, small stretches of tendons 122 and 124 under service loads can be addressed by several mathematical models that relate motor position to end effectors. However, if the mechanical structure including the end effector 110, tendons 122 and 124, and the back end mechanism 130 is highly compliant, it is between the angular position of the motor 140 (or pulley 132) and the angular position of the jaw 112. The relationship can be difficult or impossible to model with sufficient accuracy for the medical device. As a result, such systems require a control process that does not rely on a fixed relationship between a given actuator control signal and the position of the driven element.

  In the following, it should be noted that the joint of the medical device can be a pin joint structure or a structure that provides one or multiple degrees of freedom movement of the tip of the device. For example, the joint can be a continuous flexible part, or a combination of pin joints that approximate the continuous flexible part, or a single rotational joint that provides a rolling joint that is not purely rotational. For example, Cooper et al., Patent Document 1 entitled “Flexible Wrist for Surgical Tool”, Cooper et al., “Surgent Tool Haven a Positively Positioned Tendition-Multi-Distributed Patent”

  It should also be noted that in state-of-the-art medical robotic instruments, the actuator position is servo controlled to produce the desired instrument tip motion or position. Such an approach is efficient as long as the transmission system between the actuator and the instrument joint is rigid for all practical purposes. See, for example, Patent Document 3 entitled “Camera Referenced Control in a Minimally Inverse Surgical Apparatus”. Such an approach can also be used when the flexibility of the transmission system can be accurately modeled and can be a model included in a controller such as that described in US Pat. No. 6,069,097 entitled “Robotic Instrument Control System” by Barbagli et al. Can be efficient.

US Patent No. 7,320,700 US Pat. No. 6,817,974 US Pat. No. 6,424,885 US Patent Application Publication No. 2009/0012533

  In accordance with aspects of the present invention, a control system and method for a multi-degree-of-freedom instrument is provided for determining and controlling the force that a proximal actuator applies to the instrument through a series of transmission systems. Use the difference between / speed and the desired placement / speed of the instrument. The use of feedback indicating the applied force and the resulting placement of the medical device allows robotic control of the medical device even though the device's transmission system has non-negligible compliance between the proximal actuator and the remotely driven element. Enable. The feedback approach in particular allows for accurate instrument operation even when instrument placement cannot be inferred directly from the position of the proximal actuator.

  In one embodiment of the invention, the end effector or tip placement is measured or otherwise determined and the difference between the current and desired tip placement is necessary to achieve the desired tip placement. Used to determine the required joint torque and applied force. Embodiments of this control method may allow selection of dynamic behavior, for example, to facilitate instrument interaction with tissue while allowing flexibility in other parts of the instrument.

  In another embodiment of the present invention, the placement of each joint of the instrument is measured and the difference between the current and desired joint placement determines the actuator force required to move all the joints to the desired placement. Used for.

  One particular embodiment of the present invention is a medical system that includes multiple joints, actuators, and transmission systems. Each transmission system has a proximal end coupled to the actuator, each transmission system being connected to one of the associated joints to allow force transmission for articulation of the associated joint. Having a distal end coupled thereto. The sensor of the medical system measures the placement of the joint or the tip of the instrument, and the control system that operates the actuator to apply a force to the transmission system receives the measurement of the placement from the sensor and the drive applied to the transmission system Use the location measurement to determine the force.

  Another particular embodiment of the invention is a method for controlling a medical device. The method includes measuring a plurality of joint placements of the medical device, receiving instructions indicating a desired placement of the medical device, determining a tension of a transmission system that connects each actuator to the joint, and force Actuating the actuators to respectively add to the transmission system. The determination of the applied force is independent of the position of the actuator.

FIG. 1 illustrates the characteristics of a known robotic controlled medical instrument. FIG. 2 illustrates a medical device that can be manipulated using a control process according to an embodiment of the present invention that controls the force applied through a compliant transmission system to control the articulated vertebrae of the device. FIG. 3A illustrates a medical device in which a control process according to an embodiment of the present invention can operate with a transmission system having minimum and maximum force transmission to manipulate a mechanical joint. FIG. 3B shows an embodiment of the invention in which the joint includes a continuous flexible structure. FIG. 3C shows the position of a pair of tendons used to control the one degree of freedom movement of the joint of FIG. 3B. FIG. 4 schematically illustrates a robotic medical system and illustrates the quantities used in an embodiment of the present invention to control a remotely operated joint connected to an actuator through a compliant transmission system. FIG. 5A is a flowchart of a control process according to an embodiment of the present invention. FIG. 5B is a flowchart of a process for determining a tension correction value associated with the difference between actuator speed and joint speed. FIG. 5C is a flowchart of a process for determining a tension correction value associated with a difference between the speeds of actuators operating the same joint. FIG. 5D shows a function for control of maximum and minimum applied tension. FIG. 6 schematically shows a robotic medical system and in particular shows the quantities used in an embodiment of the invention for controlling a multi-joint instrument. FIG. 7A is a flowchart of a process according to an embodiment of the present invention for selecting an applied tension based on a difference between a measured joint arrangement and a desired joint arrangement. FIG. 7B is a flowchart of a process according to an embodiment of the invention that selects applied tension based on the difference between the measured tip placement and the desired tip placement. FIG. 8A is a side view of a portion of a multi-joint instrument that can be operated using drive force control according to an embodiment of the present invention that controls a joint with parallel drive axes. FIG. 8B shows a side view of a portion of a multi-joint instrument having a joint with orthogonal actuation axes that can be manipulated using drive force control according to an embodiment of the present invention. FIG. 8C shows an end view of a portion of a multi-joint instrument having a joint with orthogonal actuation axes that can be manipulated using drive force control according to an embodiment of the present invention. FIG. 9A shows an embodiment of the present invention where the joint includes a continuous flexible structure that provides two degrees of freedom movement. FIG. 9B shows an embodiment of the present invention that uses four tendons to control the two degrees of freedom movement of the joint of FIG. 9A. FIG. 9C shows an embodiment of the present invention that uses three tendons to control the two degrees of freedom movement of the joint of FIG. 9A. FIG. 9D shows an embodiment of a two-joint medical device where each joint includes a continuous flexible structure and provides two degrees of freedom movement. FIG. 9E shows an embodiment of the invention that uses six tendons to control the four degrees of freedom movement provided by the two joints of the device of FIG. 9D. FIG. 10 is a flowchart illustrating a process according to an embodiment of the invention for determining tension through continuous evaluation of joints of a multi-joint instrument.

  Use of the same reference symbols in different drawings indicates similar or identical items.

  According to one aspect of the invention, the medical device can be controlled via a transmission system that does not provide a fixed relationship between the actuator position and the joint position. In particular, the operation of the system operator (eg, surgeon) indicates the current desired placement / speed for the medical instrument, while the sensor assumes the actual placement / speed of the instrument. Force, tension, or torque is then selected according to the desired and measured arrangement and applied through the transmission system to move the instrument toward that desired arrangement. The selection criteria for applied force, tension, or torque can be changed if previous selection criteria for applied force, tension, or torque result in the joint overshooting or failing to reach the desired position.

  FIG. 2 illustrates one compliant medical device 200 having a delivery system as described in US patent application Ser. No. 12 / 494,797 entitled “Compliant Surgical Device,” which is incorporated herein by reference in its entirety. Indicates the part. Instrument 200 includes joined elements 210 that are manipulated through control of the respective tensions of tendons 222 and 224. In general, the instrument 200 may include many mechanical joints similar to the joined elements 210 and each joint may be controlled using tendons similar to tendons 222 and 224. In the exemplary embodiment, instrument 200 is an entry guide that can be manipulated to follow a patient's natural lumen. The entry guide typically includes a flexible outer sheath (not shown) that surrounds the vertebra (including element 210) through which other mechanical instruments can access the work site. One or more central lumens are provided that can be inserted into the tube. Compliance is particularly desirable in entry guides to prevent the action or reaction of the entry guide from damaging the surrounding tissue that can move or press against the entry guide. However, other types of medical devices can benefit from a compliant drive mechanism of the type shown in FIG.

  Instrument 200 includes a backend mechanism 230 that provides a compliant drive system with tendons 222 and 224 connected to joined elements 210 and drive motors 242 and 244. In particular, back end mechanism 230 includes a spring system 235 attached to tendons 222 and 224 and drive motors 242 and 244. Each spring system 235 of FIG. 2 includes a mechanical drive system 232 and a constant load spring 234. Each drive system 232 couples the motor 242 or 244 and converts the rotational motion of the drive motor 242 or 244 into a linear motion that changes the constant load applied to the tendon 222 or 224 by the accompanying constant load spring 234. In the illustrated embodiment, each constant load spring 234 includes a conventional hook law spring 236 and a cam 238. Each spring 236 connects to an associated drive system 232 such that linear movement of the drive system 232 moves the proximal end of the spring 236. Each cam 238 is supported by a first guide surface with a cable 237 attached to and supported by a distal end of an associated spring 236 thereon and a portion of a tendon 222 or 224 thereon. And a second guide surface that is moved. The guide surface of each cam 238 generally provides a different moment arm for movement of the attached cable 237 and attached tendon 222 or 224, and a tendon or draw of the tendon 220 or 224 length is attached. The tendon 222 or 224 is shaped so that the tension of the tendon 222 or 224 remains constant when the force applied by the applied spring 236 is varied. Each surface of each cam 238 is a helical surface extending for one or more rotations to provide a desired range of movement of the tendon 222 or 224 while maintaining a constant tension in the tendon 222 or 224. obtain.

  Each drive system 232 controls the position of the proximal end of the corresponding spring 236 and thus affects the amount of reference elongation of the corresponding spring 236 and the tension of the attached tendon 222 or 224. In operation, if the drive system 232 of the spring system 235 pulls the attached spring 236, the spring 236 begins to stretch, and if the element 210 and the tendon 222 or 224 attached to the spring system 235 are held securely, The force that the spring 236 applies to the cam 238 increases, thus increasing the tension of the attached cable 222 or 224. Thus, the tension of the tendon 222 or 224 is linearly determined by the movement of the proximal end of each spring 236 (according to Hooke's law, cam 238 moment arm, and spring constant of the spring 236), but for each spring system 235 behaves asymmetrically, that is, operates with a constant force in response to an external or distal force that moves the tendon 222 or 224. Constant load spring 234 and drive system 232 may alternatively be implemented in a variety of ways as further described in the aforementioned US patent application Ser. No. 12 / 494,797.

  The joined element 210 has a one degree of freedom movement (eg, rotation about an axis) and generally changes the force applied by a constant load spring 238 to which a drive motor 242 or 244 is attached. It moves when 232 is rotated. However, this drive mechanism is compliant so that external forces can move element 210 without a corresponding rotation of drive system 232. As a result, there is no fixed relationship between the position or orientation of the joined elements 210 and the position of the drive system 232 or drive motor 242. In accordance with an aspect of the present invention, the control system 250 uses a sensor 260 to measure the orientation of the element 210. The sensor 260 can be, for example, a shape sensor that senses the shape of the element 210 joined along the length of the instrument 200 that includes the element 210. Some examples of shape sensors are described in US Patent Application Publication No. 2007 / 0156019A1 (p. Jul. 20, 2006, e.g. e. P. E. E. P. E. E., 2007), published by Larkin et al., Entitled “Robotic Surgical System Inclusion Position Sensors Using Fiber Bragg Grattings”. US Patent Application No. 12 / 164,829 (filed June 30, 2008) entitled “Fiber optical shape sensor” by Prisco, both of which are incorporated herein by reference. However, any sensor that can measure the angular position of the joined element 210 can alternatively be used. Further, the control process described below uses such measurements for the calculation of the applied force required to operate the joined element 210.

  The instrument 200 has a “backdriving” capability when the backend mechanism 230 is removed from the motor pack, and the constant load spring 235 still prevents the tendons 222 and 224 from loosening and the distal portion of the instrument Can be manually placed (or taken in some posture) without damaging the back-end mechanism 230 or creating slack in the tendons 222 or 224. This “back-driving” capability is generally associated with surgical instruments, particularly instruments with a flexible main tube that can be bent or manipulated during instrument insertion while the instrument is not under active control by the control system 250. This is a desirable characteristic. For example, the instrument 200 can be manually brought into a certain position and the tendons in the main shaft do not suffer from excessive tension or loosening.

  Another example of a compliant delivery system for a medical device joint is shown in FIG. 3A. FIG. 3A shows the drive during operation of the instrument as described in US patent application Ser. No. 12 / 286,644 entitled “Passive Preload and Capstan Drive for Surgical Instruments”, which is incorporated herein by reference in its entirety. FIG. 9 illustrates an exemplary embodiment of a medical device 300 that uses a drive process that allows the motor to rotate freely or allow the drive tendon to slip relative to the drive motor. The medical device 300 has an end effector 310 at the end of the main tube 320, and a back end mechanism 330 extends through the main tube 320 to control one degree of freedom movement of the end effector 310. And 324 are operated. In the illustrated embodiment, tendons 322 and 324 attach to the mechanical members of end effector 310 such that the tension of tendons 322 and 324 facilitates rotating end effector 310 in the opposite direction about the pivot joint structure.

  The joint structure of FIG. 3A is merely an example, and other joint structures that provide one degree of freedom of motion in response to the tension applied to a set of tendons can be used in alternative embodiments of the present invention. For example, FIG. 3B is commonly found in catheters, gastrointestinal tract, colon, and bronchial endoscopes, guidewires, or other endoscopic instruments such as grasping devices and needles used for tissue sampling, for example. An embodiment of such a joint 310 is shown.

  This can bend or bend depending on the force applied through tendons 322 and 324. The catheter joint may simply include an extrusion of a plastic material that bends in response to the difference in tension between tendons 322 and 324. In one configuration, tendons 322 and 324 extend through a lumen in the catheter and attach to the end of the catheter, as shown in FIG. 3C. Thus, the forces of tendons 322 and 324 can be used to bend the catheter in a direction that depends on tendons 322 or 324 having greater tension. Catheter bending can be used, for example, to guide the catheter during insertion. In the embodiment of FIG. 3B, the distal end sensor 360 may measure the bending angle of the distal portion of the catheter in order to measure or calculate the “joint” angle and velocity. In one particular embodiment, the bending angle may be defined as the orientation of the catheter tip relative to the base of the distal flexible portion of the catheter. The backend and control architecture for the catheter joint 310 of FIG. 3B is such that the measured joint angle and speed are multiplied by the distance and the distance between the actuator cable lumen and the center of the distal flexible section to It can be identical to that of the embodiment of FIG. 3A, except that it can be converted.

  At the proximal end of the main tube 320, the back end mechanism 330 converts the torque applied by the drive motors 342 and 344 to the tension of the respective tendons 322 and 324 and the force or torque applied to the drive joint of the end effector 310. Acts as a transmission part. In the illustrated embodiment, the drive motors 342 and 344 may be direct drive electric motors that are directly coupled to capstans 332 and 334 about which the respective tendons 322 and 324 wrap around. In particular, a tendon 322 is wound around a corresponding capstan 332 with a wrap angle set (less than a full rotation or as large as one or more rotations) and is not fixed to the capstan 332 Has an end extending from the capstan 332 to the passive preload system 333. Similarly, tendon 324 has an end that wraps at a wrap angle set around a corresponding capstan 334 and extends from capstan 334 to passive preload system 335. Because the tendons 322 and 324 need not be permanently attached to the capstans 332 and 334, the tendons 322 and 324 are connected to the capstans 332 and 334 and to the drive motors 342 and 334 respectively coupled to the capstans 332 and 334. Can slide about 344 axes.

  The proximal ends of tendons 322 and 324 are associated with respective passive preload systems 333 and 335, each implemented as a cam and hook law spring that act together as a constant load spring in FIG. 3A. Passive preload systems 333 and 335 are biased so that systems 332 and 334 apply a non-zero force or tension to tendons 322 and 324 throughout the range of movement of instrument 300. Using this structure, the capstans 332 and 334 can rotate freely and the passive preload systems 333 and 335 control the tension of the tendons 322 and 324 and retract the required lengths of tendons 322 and 324 or Avoid loosening of tendons 322 and 324 by paying out. When the backend mechanism 330 is removed from the motors 342 and 344, the passive preload systems 333 and 335 still prevent the tendons 322 and 324 from loosening and the main tube 320 (if it is flexible) into the backend mechanism 330. Allows manual placement (or some posture) without damaging or creating a slack in tendons 322 or 324. Thus, instrument 300 also has a “back-driving” capability similar to that described above with respect to instrument 200 of FIG.

  End effector 310 may be operated using drive motors 342 and 344 under active control of control system 350 and human inputs (eg, master control inputs in a master-slave servo control system). For example, when the motor 342 draws the tendon 322, the motor torque is transmitted as an applied tension at the distal portion of the tendon 322. (The maximum tension that the capstan 332 can apply to the proximal portion of the tendon 322 depends on the tension at which the tendon 322 begins to slide relative to the capstan 332, but in general, the maximum tension actually used is 322 and 324 may be selected to prevent sliding the capstans 332 and 334.) At the same time, when the power to the motor 344 stops and allows the motor 344 and the capstan 334 to rotate freely, the tendon 324 Can be kept at a minimum tension, which is a constant load that the passive preload system 335 applies through the capstan 334 to the proximal end of the tendon 324. Greater tension in tendon 322 tends to cause end effector 310 to rotate counterclockwise in FIG. 3A. Similarly, stopping power to motor 342 and applying power to motor 344 to apply force to end effector 310 through tendon 324 tends to cause end effector 310 to rotate clockwise in FIG. 3A. The ability of the motors 342 and 344 to rotate freely while the tendons 322 and 324 are under tension and the allowance of the tendons 322 and 324 to slip on the capstans 332 and 334 are determined by the control system 350 in terms of the angle of the motor 340 and the end effector 310. Do not allow reliance on fixed relationships between positions. However, the control system 350 can use the sensor 360 to measure the angular position of the end effector 310 relative to the joint driven through tendons 322 and 324.

  The instrument of FIGS. 2, 3A, and 3B may have a transmission system between the actuator that provides compliance and the driven joint, which is particularly desirable for instruments with a flexible main tube. However, compliant delivery systems can also exist in conventional instruments. For example, the known instrument of FIG. 1 may use a covering or bowden cable in the part of the instrument that bends and a rod element in the straight part. The rod element can reduce stretching that interferes with the direct relationship of actuator and joint position. However, in some applications, it may be desirable to use tender materials of softer material (eg, polymer tendons where electrical insulation or minimal friction is desired), such tendons may be used in actuators and joints. For a control process that relies on a direct relationship between positions, it can result in an unacceptable amount of elongation. Solid steel that pulls the wire may also be used in or as a transmission system.

  According to aspects of the present invention, the control process for the medical device of FIGS. 2, 3A, and 3B or other compliant transmission system may be applied to drive a mechanical joint. Telemetry of mechanical joint positions can be used to determine. The control process can also be used for instruments having a rigid transmission system. FIG. 4 schematically illustrates the concept of a medical device 400 having a mechanical joint 410 having a one degree of freedom movement corresponding to an angle or position θ. Position terminology is used broadly herein to include Cartesian coordinate position, angular position, or other representation of a one degree of freedom configuration of a mechanical system. A sensor (not shown) measures the position θ at the remote joint 410 and sends the measured position θ to the control system 450, eg, from the sensor at the distal end of the instrument 400 to the instrument main tube (not shown). ) Through a signal line (not shown) that extends to the control system 450 at the proximal end of the instrument. The sensor may additionally measure a velocity dθ / dt related to the movement of the joint 410, or the velocity dθ / dt may be determined from two or more measurements of the position θ and the time between the measurements.

  The joint 410 is connected to the actuator 440 through the transmission system 420 such that the joint 410 is away from the actuator 440, for example, the actuator 440 may be at the proximal end of the instrument while the joint 410 may be at the distal end of the instrument. Connected. In the illustrated embodiment, the transmission system 420 connects to the joint 410 such that the tension T applied to the transmission system 420 by the actuator 440 tends to rotate the joint 410 in a clockwise direction. In general, the transmission system 420 includes the entire mechanism used to transmit force from the actuator 440 to the joint 410, and the actuator 440 provides the tension to the cable or other components of the transmission system 420. A force or torque can be applied to the. However, since such tension is generally proportional to the applied force or torque, the term tension is intended here to be used to indicate force or torque without loss of generality. It should also be noted that the transmission system 420 is (although not necessary) so compliant that the direct relationship between the position of the joint 410 and the position of the actuator 440 is not accurate enough for control of the joint 410. It is. For example, the transmission system 420 can be stretched between the minimum and maximum tensions T applied to the transmission system 420 such that the difference in effective length of the transmission system 420 can correspond to 45 ° of the joint of the joint. On the other hand, typical medical devices allow for an elongation corresponding to an angle less than a few degrees of the joint of the joint so that the position of the joint can be accurately modeled based on the actuator position. In the general case, it should be understood that compliance is not limited to the extension in the direction of a simple hook of the spring structure. Transmission system 420 may include, for example, tendon 222 and at least a portion of backend mechanism 230 in the embodiment of FIG. 2 or tendon 322 and at least a portion of backend mechanism 330 in the embodiment of FIG. 3A. In general, the response of the transmission system 420 to tension T applied to the proximal end of the transmission system 420 and to external forces applied along the length of the joint 410 or transmission system 420 is difficult to model. Can be.

  The actuator 440, which may include the drive motor 242 or 342 of FIG. 2 or 3A, applies tension T to the proximal end of the transmission system 420 and applies force or torque to the joint 410 through the transmission system 420, but other forces. Alternatively, torque is also applied to the joint 410. In particular, one or more other transmission systems 420 may be connected to the joint 410 and apply net tension or force that tends to rotate the joint 410 as a whole. In the illustrated embodiment of FIG. 4, the transmission system 442 is such that the tension of the transmission system 442 tends to oppose the applied tension T and tends to rotate the joint 410 counterclockwise in FIG. The joint 410 and the drive motor 442 are connected to each other. The transmission system connected to the additional transmission system 422 or the joint 410 can be the same as the transmission system 420, except for the difference that the transmission system 422 connects to the joint 410.

The control system 450 can be a general purpose computer or wired circuit that executes a program to generate a drive signal that controls the tension T that the actuator 440 applies to the transmission system 420. If actuator 440 is an electric motor, the drive signal can be a drive voltage or current that controls the torque output from actuator 440 and tension T is divided by an effective moment arm where tension T is applied to transmission system 420. Is equal to the motor torque As described further below, the control system 450 may include one or more of a desired position θ _D for the joint 410, a desired velocity dθ _D / dt, and a position θ for the joint 410 at current and previous times. The measured value can be used to calculate the magnitude of the tension T or motor torque. A user (eg, a surgeon controlling system 400) may provide desired position θ _D and velocity dθ _D / dt by manipulating controller 460. The exact configuration of the controller 460 is not critical to the present invention, except that the controller 460 can provide signals from which values for the desired position θ _D and velocity dθ _D / dt can be determined. Manual controllers are suitable for complex medical instruments that typically provide signals indicative of many simultaneous instructions regarding the movement of the medical instrument, such movement acting on multiple joints of the instrument. Suitable manipulators for use as the controller 460 are, for example, Intuit Surgical, Inc. It is given to the master controller of da Vinci Surgical System available from

Tension T required to move the joint 410 from theta current measured position at the desired location theta _D in the time interval Δt generally depends on many factors, including: the joint to resist the applied tension T 410, the inertia of the actuator 440 applying the tension T, any other transmission system 422 coupled to the joint 410 and applying an effective force of the body, the external force applied to the joint 410, the driving or transmission of the joint 410 Internal and external frictional forces against system movement, current speed dθ / dt of joint 410, and internal and external damping forces. Many of these factors can vary depending on the operating environment of the instrument 400 and can be difficult to measure or model. However, the model can be developed empirically based on the dynamics of the system or for a particular joint of the medical device. In one particular embodiment, the control system 450 determines the tension T between the measured and desired positions of the joint 410 and the measured and desired speeds of the joint 410, respectively. The difference is determined from the error (θ _D −θ) and (dθ _D / dt−dθ / dt) of the distal joint.

FIG. 5A is a flowchart of a process 500 for controlling a medical device having the basic structure of the system 400 of FIG. Process 500 begins at step 510 by reading the current value of joint 410 position θ and determining the current value for joint velocity dθ / dt. The velocity dθ / dt can be measured or determined directly or using the current position θ, the previous position θ ′, the time interval Δt between measurements, eg under the assumption of a constant velocity (eg dθ / Dt = (θ−θ ′) / Δt) or can be approximated in a well known manner under the assumption of constant acceleration given a previous determination of velocity. Step 515 then obtains the desired position θ _D and the desired velocity dθ _D / dt for joint 410, and step 520 determines the difference or error (θ _D −θ between the measured position and the desired position. ) And the difference or error (dθ _D / dt−dθ / dt) between the measured speed and the desired speed.

Errors in calculated position and speed in step 520 may be used to determine the tension T that is required for joint 410 to reach the desired location theta _D. In the embodiment of FIG. 5A, the applied tension T may include multiple contributions, with the primary contribution being a function f _{1 of} position error (θ _D −θ) and velocity error (dθ _D / dt−dθ / dt). _Is the distal tension _TDIST , determined as The distal tension T _DIST is independent of the position of the actuator, eg, the angle of the motor shaft, which is that even if there is no direct relationship between the position of the joint 410 and the position of the actuator 440. Allows determination of _DIST . In one particular embodiment, the function f ₁ is of the form of Equation 1, g1 and g2 are gain factors, C is a constant or shape dependent parameter, and T _sign is a sign, ie ± 1. The sign T _sign is associated with the movement of the joint 410 created by the tension of the transmission system 420, for example, can be positive (eg, +1) when the tension T of the transmission system 420 tends to increase the position coordinate θ, and It can be negative (eg, −1) when the tension T of the transmission system 420 tends to decrease the position coordinate θ. In other embodiments, the function f ₁ forces a lower bound on the force so that, for example, the force is always positive and sufficient to avoid slack in the transmission system. Parameter C may be a constant selected according to known or modeled forces applied to joint 410 by other parts of the system. For example, the parameter C may be a constant selected to balance the torque provided by other transmission systems that apply forces to the joint 410, or may correspond to an expected friction or external force. However, the parameter C need not be strictly constant and can include non-constant terms that compensate for properties such as gravity or mechanical stiffness that can be effectively modeled, and therefore the parameter C can be measured at the measured joint. It can depend on position or speed. Gain factors g1 and g2 may be selected according to the desired stiffness and damping of joint 410. In particular, when the joint 410 is used as a static gripper, the net gripping force or torque applied to the tissue is determined by the term g1 (θ _D −θ) of Equation 1. In general, the gain factors g1 and g2 and the constant C may be selected according to the desired stiffness and damping or responsiveness of the joint 410 or according to error accumulation. For example, when the instrument 400 is inserted to follow a natural lumen in the patient, the gain factor g1 is low so that the joint 410 behaves gently and prevents the joint 410 from damaging surrounding tissue. Can be set to a value. After insertion, the gain factor g1 can be set to a high value that allows the surgeon to perform an accurate surgical task with the instrument.
Formula 1: F ₁ = T _sign * (g 1 (θ _D −θ) + g 2 (dθ _D / dt−dθ / dt) + C)
The term g 1 (θ _D −θ) + g 2 (dθ _D / dt−dθ / dt) + C in Equation 1 causes the joint 410 to reach the desired position θ _D at a given time Δt using the transmission system 420. It can be used to approximately determine the torque, tension, or force currently required at the joint 410 to rotate. Torque and force or tension are related to the torque being the product of force and effective moment arm R, and this effective moment arm is between the connection to joint 410 of transmission system 420 and the axis of rotation of joint 410. Defined by vertical distance. The effective moment arm R can be absorbed by the gain factors g1 and g2 and the constant C or can be used to convert the calculated distal tension T _DIST into a calculated torque.

With appropriate selection of function f ₁ , eg, appropriate selection of parameters g 1, g 2 and C of Equation 1, the distal tension T _DIST is determined in a manner that the actuator 440 is _{responsive to} the human operator's operation of the manual controller 460. The force required to apply to move joint 410 can be approximated. However, optional correction values may be provided by steps 530, 535, 540 and 545 under some circumstances. In particular, optional steps 530 and 535 each calculate the sum or integral I of the saturation of the position error (θ _D −θ) and the integral tension T _INT . The integral tension T _INT , which can be positive, zero, or negative, can be added as a correction value for the distal tension T _DIST calculated in step 525. The integral tension T _INT can be calculated as a function f ₂ of the saturated integral I and can simply be the product of the integral I and the gain factor. The saturated integral I calculated in step 530 is simply the position error (θ _D −θ) of the past N intervals or the measured position at the end of the interval and the desired position that should have been achieved. It can be the sum of the difference between (θ _{D, i} −θ _i−1 ). The number N of intervals included in the sum may or may not be limited and the integral I may be saturated in that the magnitude of the integral is not allowed to exceed the maximum saturation value. The saturation value can generally be selected to limit the maximum or minimum value of the integral tension _TINT . However, the maximum or minimum value of the integral tension T _INT is alternatively, may be limited when calculating the value of the function f _2.

Optional step 540 calculates the proximal tension T _PROX and other correction values represented herein. This proximal tension can be positive, zero, or negative. The proximal tension T _PROX can be added to the distal tension T _DIST calculated in step 525. FIG. 5B is a flowchart of a process for calculating the proximal tension T _PROX . Process 540 begins at step 542 by reading the current value of actuator 440 velocity dθ _A / dt. The velocity dθ _A / dt can be measured with a standard tachometer attached to the base of the actuator 440. In order to improve computational efficiency, step 542 may also be planned to execute between steps 510 and 515 of FIG. 5A. Step 544 then calculates a proximal speed difference or error _{de PROX} / dt, the proximal speed difference or error _{de PROX} / dt is the desired speed desired speed d [theta] / was calculated based on the dt of the joint 410 It is defined as the difference or error between the current speed calculated based on the current actuator speed dθ _A / dt. In one particular embodiment, the desired speed can be the product of the effective moment arm R, the sign T _sign , and the desired speed dθ _D / dt of the joint 410, while the current speed is the effective moment arm and actuator of the actuator 440. It can be the product of the velocity dθ _A / dt. In the embodiment of FIG. 5B, the proximal tension T _PROX is determined as a function f ₄ of the proximal velocity error de _PROX / dt. In one particular embodiment, the function f ₄ can simply be the product of the proximal velocity error de _PROX / dt and the gain factor. The gain factor may be selected to provide an additional damping effect for the transmission system 420.

Optional step 550 of FIG. 5A calculates the anti-tension _TPAIR . This counter-tension _TPAIR can be a correction value for positive, zero, or negative distal tension _TDIST . This distal tension _TDIST was calculated at step 525. FIG. 5C is a flowchart of a process 550 for calculating the counter tension _TPAIR . Process 550 begins at step 552 by reading the current value of actuator 440 velocity dθ _A / dt and the velocity values of all other actuators associated with joint 410. In the system of FIG. 4, there are two actuators 440 and 442 coupled to joint 410 and two actuator velocities dθ _A / dt and dθ _{A ′} / dt. Step 552 may also be planned to execute between steps 510 and 515 of FIG. 5A. Step 556 then calculates a pair speed difference or error _{de PAIR} / dt, the pair speed difference or error _{de PAIR} / dt, when the actuator 440 and 442 are substantially identical, for example, each transmission system Is defined as the difference or error between the current velocities dθ _A / dt and dθ _{A ′} / dt of the actuators 440 and 442 associated with the joint 410. In one particular embodiment, the current speed error de _PAIR / dt may be the product of the difference (dθ _A / dt−dθ _{A ′} / dt) and the effective moment arm of actuators 440 and 442. In the embodiment of FIG. 5C, the counter tension T _PAIR is determined as a function f ₅ of the speed error de _PAIR / dt. In one particular embodiment, the function f ₅ may simply be the product of the speed error de _PAIR / dt and the gain factor. The gain factor may be selected to provide an additional damping effect for the transmission system 420.

Tension T is determined in step 560 of FIG. 5A as a function of the sum of distal tension T _DIST , proximal tension T _PROX , versus tension T _PAIR and integral tension T _INT . In the embodiment of FIG. 5D, function f ₃ limits the maximum and minimum values of tension T. The maximum tension T _MAX and the minimum tension T _MIN can be set in the control system 450 program (eg, in software). However, the compliant system itself may have minimum or maximum tension using an appropriate design of the backend mechanism. For example, the transmission system shown in FIG. 3A includes a minimum tension T _MIN that is controlled by the settings of the preload system 333 or 335 when the motor / actuator 342 or 344 rotates freely, and the torque of the couple motor 342 or 344. However, if the tendon 322 or 324 exceeds the level at which the capstan 332 or 334 slides, it has a maximum tension T _MAX resulting from the slip. In general, it is desirable to have maximum and minimum tensions T _MAX and T _MIN set by both hardware and software. In particular, the maximum tension T _MAX should be set so as to avoid damage to the instrument caused by high forces, and the tension T _MIN ensures that the tendon of the transmission system does not loosen and come off or become entangled. Should be set to

Step 565 of FIG. 5A generates a control signal that causes the actuator 440 to apply the tension T calculated in step 560. For example, the control signal may be a drive current that is controlled to be proportional to the calculated tension T when the actuator 440 is a direct drive electric motor. The control system 450 in step 570, during the time interval Δt to the actuator 440, is held together causing added calculated tension T, during this time, the joint 410 moves towards the current desired position theta _D. When the tension T changes, the application of complete tension T is delayed by a certain time depending on the inertia of the actuator 440. Preferably, the inertia of actuator 440 is relatively small for quick response. For example, the inertia of the drive motor that operates as the actuator 440 is preferably less than five times the inertia of the joint 410. After time Δt, process 500 branches back to step 510 to repeat the joint position measurement, target position and velocity acquisition, and calculation of the tension T that will be applied during the next time interval. In general, the time Δt should be small enough to provide a movement that appears smooth to the instrument operator and does not cause unwanted vibration of the instrument. For example, the calculation and setting of the tension T 250 times per second or more provides movements that appear smooth to the human eye and also allows the operation of the instrument in response to human commands, such as the human operation of the controller 460. provide. The use of errors in the calculation of tension T generally causes joint 410 to converge to the desired position with or without calculation of integral tension T _INT and without detailed modeling or measurement of the instrument or external environment. However, as described above, the parameters such as gains g1 and g2 used to calculate the applied tension T can be adjusted for a particular instrument and further used to compensate for changes in the instrument's external environment. Can be adjusted inside.

The tension that the actuator 442 applies to the transmission system 422 can also be controlled using the control process 500 of FIG. 5A, and the parameters used in the process 500 for the actuator 442 and the transmission system 422 are the actuator 440 and the transmission system. Based on the similarities and differences of actuator 442 and transmission system 422 as compared to 420, the same or different one used for actuator 440 and transmission system 420 may be used. In particular, the sign value T _sign for the actuator 442 in the configuration of FIG. 4 is opposite to the sign value T _sign for the actuator 440 because the transmission systems 422 and 420 connect to rotate the joint 410 in the opposite direction. become. As a result, the main contribution contribution T _DIST calculated in step 525 is typically negative for one actuator 440 or 442. Step 560 of calculating the applied tension T may set the total negative tension T _DIST + T _PROX + T _PAIR + T _INT to the minimum tension T _MIN shown in FIG. 5D. Thus, the parameters for the calculation of the distal tension T _DIST in step 525, eg, the constant C, can generally be selected based on the assumption that other actuators apply the minimum tension T _MIN .

The principles described above for control of a single joint of a medical device can also be used to control multiple joints of the device simultaneously. FIG. 6 schematically illustrates several quantities used in the multi-joint medical device 600 and the control process for the device 600. Instrument 600 includes L joints 610-1 through 610 -L, collectively referred to herein as joints 610. Each joint 610 provides a range of relative positions or orientations of adjacent mechanical members and typically has one or two degrees of freedom movement, as further described below. The joint 610 of the instrument 600 provides N degrees of freedom at the front, where the number of degrees of freedom N is greater than or equal to the number of joints L, and the degree of freedom of the structure of the joint 610 is described using the N component or vector θ. obtain. The N component velocity vector dθ / dt is related to the vector θ. The torques τ _{1 to} τ _N that move the joints 610-1 to 610 -L are respectively _N components of the vector θ in that the torques τ _{1 to} τ _N tend to change the components of the respective vectors θ. Correspond.

Joint 610 includes M transmission systems 620-1 through 620 -M (generically referred to herein as transmission system 620) and M actuators 640-1 through 640 -M (generally referred to herein as actuator 640). It is driven using Transmission system 620 and actuator 640 may be similar or identical to transmission system 420 and actuator 440 described above with reference to FIG. In general, the number M of transmission systems 620 and actuators 640 is greater than the number N of degrees of freedom, but the relationship between M and N depends on the particular medical instrument and instrument joint mechanism. For example, a joint 610 that provides one degree of freedom motion can be driven using two transmission systems 620 and a joint 610 that provides two degrees of freedom can be driven using three or four transmission systems 620. . Other relationships between degrees of freedom and drive transmission systems are possible. The control system 650 operates the actuators 640-1 to 640- _M to select the respective tensions T _{1 to} T _M that the actuators 640-1 to 640-M apply to the transmission systems 620-1 to 620-M, respectively. To do.

The control system 650 for the instrument 600 may use a distal sensor (not shown) to determine the position and velocity vectors θ and dθ / dt associated with the joint 610. (Position and velocity are used herein to include linear and angular coordinate values and motion.) Control system 650 also determines the desired position and velocity vectors θ _D and dθ _D / dt of joint 610. . As described further below, the desired position and velocity vectors θ _D and dθ _D / dt depend on input from a manual controller that can be manipulated by the surgeon using the instrument 600. In general, the desired position and velocity vectors θ _D and dθ _D / dt are further determined by criteria or restrictions set in the control process implemented using the control system 650.

FIG. 7 illustrates a control process 700 according to an embodiment of the present invention for controlling a multi-joint instrument such as instrument 600 of FIG. Process 700 begins at step 710 by reading joint position vector θ from one or more sensors of the instrument. The velocity vector dθ _D / dt can be determined using direct measurement of joint motion or through calculation of changes in position measurements between two time points. Control system 650 receives the surgeon's instructions at step 715. The surgeon's instructions may indicate the desired position and speed of a particular working part of the instrument. For example, through operation of the manual controller 660, the surgeon is as described in US Pat. No. 6,493,608, entitled “Aspects of a Control System of a Minimal Inverse Surgical Apparatus”, which is incorporated herein by reference. May indicate the desired position, velocity, orientation, and rotation of the distal end or end effector of the instrument. Step 720 then converts the instructions from the manual controller and rotor 660 to the desired position and velocity vectors θ _D and dθ _D / dt of joint 610. For example, given the desired position, orientation, velocity, and angular velocity of the distal tip of the instrument 600 of FIG. 6, the control system 650 can determine the desired joint position and velocity vectors θ _D and dθ that achieve the desired tip placement. _D / dt can be calculated. The transformation step 720 is described in “Modeling and Control of Robot Manipulators,” L. Sciavico and B.M. Siciliano, Springer, 2000, pp. 104-106 and "Springer Handbook of Robotics," Bruno Siciliano & Ossama Khatib, Editors, Springer, 2008, pp. It can be achieved using well known techniques such as the differential kinematic inverse described in 27-29. U.S. Pat. No. 6,493,608, named “Aspects of a Control System of a Minimally Inverse Surgical Apparatus”, also describes the desired joint position and velocity vectors θ _D and dθ _D / dt to achieve the desired tip placement. Describe techniques for determining For instruments with kinematic redundancy, i.e., if the number of motion degrees of freedom provided by joint 610 is greater than the number of commanded motion degrees of freedom specified by manual controller 660, the redundancy is determined by Yoshihiko Nakamura. It should be noted that it can be solved with standard techniques such as those described in "Advanced Robotics: Redundancy and Optimization," Addison-Wesley (1991).

  It should also be understood that software constraints between instrument joints can also be implemented when solving inverse kinematic problems with respect to the desired command for the instrument. For example, the joint position and velocity commands of the two joints can be forced to be the same or opposite or some ratio, effectively realizing a virtual cam mechanism between the joints.

Step 725 calculates a position error vector (θ _D −θ) and a velocity error vector (dθ _D / dt−dθ / dt), and step 730 calculates the respective torque components τ _{1 to} τ _N. The components of the error vectors (θ _D −θ) and (dθ _D / dt−dθ / dt) are used. In one particular embodiment, each torque component τ _i for subscript i from 1 to N is determined using Equation 2. In Equation 2, g1 _i and g2 _i are gain factors, and C _i is a shape dependent parameter that can be selected according to a constant or a known or modeled force applied to the joint by other parts of the system. However, the parameter C _i need not be strictly constant, but can include non-constant terms that compensate for properties such as gravity or mechanical stiffness that can be effectively modeled, and thus C _i is the torque τ _i. May depend on the measured position or velocity of the joint 610-i on which the acts. Generally, the gain coefficients g1 _i and g2 _i and constants C _i in accordance with the desired stiffness and damping or responsiveness of the joint, or may be selected according to the accumulation of errors. For example, when the instrument 600 is inserted to follow a natural lumen in a patient, the gain factor g1 _i is low enough to cause the joint to behave gently and prevent the joint from damaging surrounding tissue. Can be set to After insertion, the gain factor g1 _i can be set to a high value that allows the surgeon to perform an accurate surgical task with the instrument. Other equations or modified values of Equation 2 can be used to determine torque. For example, the calculated torque may include a correction value that is proportional to the saturation integral of the difference between the current measurement of the joint position and the desired joint position that the previously applied torque is intended to achieve. . Such a correction value using saturation integration may be determined as described in connection with the single joint control process of FIG. 5A, particularly as shown in steps 530 and 535 of FIG. 5A.
Formula 2: τ _i = g 1 _i (θ _D −θ) _i + g 2 _i (dθ _D / dt−dθ / dt) _i + C _i
Step 735 uses the torque calculated in step 730 to determine the distal tension _TDIST . The distal tension _TDIST is an M-component vector corresponding to the transmission systems 620-1 to 620-M and actuators 640-1 to 640-M. The determination of the distal tension depends on the geometry or mechanism between the instrument joint and the transmission system. In particular, in a multi-joint, each joint can be affected not only by the force applied directly by the transmission system attached to the joint, but also by a transmission system that connects to the joint near the distal end of the instrument. Torque and tension in a medical device can be modeled using an equation of the form of Equation 3 in general. In Equation 3, τ _{1 to} τ _N are components of the torque vector, and T _{1 to} T _M are the distal tensions of each of the M transmission systems that articulate the joint 610. Each coefficient a _IJ with subscript I = 1 to N and subscript J = 1 to M generally corresponds to the effective moment arm of the rotating shaft corresponding to joint tension T _J and torque τ _I.

Formula 3:

したがって、ステップ７３５での計算は、Ｍ個の変数Ｔ_１乃至Ｔ_Ｍに対するＮ個の方程式を解くことに対応する。Ｍは概してＮより大きいので、解は一意的ではなく、したがって、全ての張力が最小値のセットより大きいという制約等の、不等式の制約が選択されることができ、最も低い最大値のセットが選択されるという条件等の、最適性条件が、全ての又は選択されたジョイントにおける所望の閾値より上に留まる最小張力のような所望の特性を持つ一意的な解を提供するために適用され得る。最小の張力の制約等不等式及び最適性条件を伴う式３の逆行列問題は、線形計画法のシンプレックス法等の幾つかの良く知られた技法によって解かれ得る。（例えば、その全体が参照により本願に援用される、"Ｌｉｎｅａｒ Ｐｒｏｇｒａｍｍｉｎｇ １： Ｉｎｔｒｏｄｕｃｔｉｏｎ，" Ｇｅｏｒｇｅ Ｂ． Ｄａｎｔｚｉｇ ａｎｄ Ｍｕｋｕｎｄ Ｎ． Ｔｈａｐａ， Ｓｐｒｉｎｇｅｒ−Ｖｅｒｌａｇ， １９９７を参照。）本発明のさらなる態様によれば、遠位張力は、最も遠位のジョイントとから始まるジョイントを連続して評価する（調べる、数値を求める）とともに幾何学的パラメータ及びより遠位のジョイントに関して以前に計算された張力に基づいて各ジョイントに接続する伝達システムにおける張力を解くプロセスを使用して決定され得る。

Accordingly, the calculation at step 735 corresponds to solving N equations for _M variables T ₁ through T _M. Since M is generally greater than N, the solution is not unique, so an inequality constraint can be chosen, such as the constraint that all tensions are greater than the minimum set, and the lowest set of maximum values is Optimality conditions, such as being selected, can be applied to provide a unique solution with the desired properties such as minimum tension that stays above the desired threshold at all or selected joints. . The inverse matrix problem of Equation 3 with minimum tension constraint inequality and optimality conditions can be solved by several well-known techniques such as the simplex method of linear programming. (See, for example, “Linear Programming 1: Introduction,” George B. Dantzig and Munkd N. Tapa, Springer-Verlag, 1997, which is incorporated herein by reference in its entirety.) According to a further aspect of the invention. Distal tension continuously evaluates (examines, finds a numerical value) the joints starting with the most distal joint and each joint based on geometric parameters and tensions previously calculated for more distal joints Can be determined using a process of relieving tension in the transmission system connected to.

The control system 650 in one embodiment of the process 700 moves the actuators 640 to apply the distal tension calculated at step 735 to each transmission system 620. Alternatively, the distal tension correction value may be determined as shown in steps 740 and 745. In particular, step 740 calculates a corrected tension T _PROX . This corrected tension T _PROX is calculated based on the desired transmission speed vector dθ _DL / dt calculated based on the desired joint speed dθ _D / dt and the current actuator speed dθ _A / dt. It is determined by the difference between the transmission velocity vector dθ _L / dt. In one particular embodiment, the desired transmission speed may be the product of the transposed matrix of the coupling matrix A of Equation 3 with the desired joint speed dθ _D / dt, while the current transmission speed is the actuator speed dθ _A. / Dt and the product of each moment arm of the actuator 640. The corrected tension T _PROX can compensate for inertia or other effects between the actuator 640 and the joint 610 connected, and in one embodiment, the difference (dθ _DL / dt−dθ _L / dt) and gain. It is a function of a difference (dθ _DL / dt−dθ _L / dt) such as a product of coefficients. Step 745 calculates the corrected tension _{T PAIR,} the corrected tension _{T PAIR} is determined by the difference between the speed of the actuator for driving the same joint. For example, if the joint is driven by a pair of actuators that provide one degree of freedom movement and is connected to the joint through a pair of transmission systems, the modified tension T _PAIR is a function of the difference between the speeds of the two actuators. Can be determined as (See, for example, step 550 in FIG. 5A above.) A correction value similar to the correction tension T _PAIR is generally used when more than two transmission systems and actuators drive a joint with two degrees of freedom. Can be

Step 750 combines the distal tension T _DIST with any modified tension T _PROX or T _PAIR to determine the combined tension T applied by the actuator. In general, each component T ₁ -T _M of the combined tension T is calculated as the desired maximum value calculated above with reference to FIG. 5D, or the sum of the calculated distal tension T _{DIST and the} modified tensions T _PROX and T _PAIR . If greater or less than the minimum value, it can be limited to saturate to the maximum tension T _MAX or the minimum tension T _MIN . Steps 755 and 769 then actuate the actuator 640 to apply and hold the combined tension T for a time interval Δt before the process 700 returns to step 710 and reads a new joint position. Maintaining tension for an interval of approximately 4 ms or less, corresponding to a speed of 250 Hz or higher, can result in smooth movement of the instrument for medical procedures.

  Medical instruments generally require that the working tip or end effector of the instrument have a position and orientation that can be controlled by an operator, such as a surgeon. On the other hand, the particular position and orientation of each joint is not important to the procedure commonly performed, except where the joint position or orientation is forced by the lumen through which the instrument extends. In accordance with aspects of the present invention, one approach for controlling a multi-joint instrument selects the tension applied through the tendon using the difference between the current and desired placement of the instrument tip. For example, the difference between the measured position, orientation, speed, and angular velocity of the instrument tip and the desired position, orientation, speed, and angular velocity of the instrument tip is the tension applied to the tendon of the medical instrument. Can be controlled.

  FIG. 7B illustrates a control process 700B according to an embodiment of the invention. Process 700B uses the same steps as several processes 700, and these steps have the same reference numbers in FIGS. 7A and 7B. Process 700B reads or determines the joint position θ and joint velocity dθ / dt from one or more sensors of the medical instrument at step 710 and determines the position, orientation, velocity, and angular velocity of the instrument tip at step 712. Read or determine. The tip here represents the specific mechanical structure of the instrument and may be an end effector such as a forceps, scissors, scalpel, or cautery device at the distal end of the instrument. In general, the tip has 6 degrees of freedom movement, with six component values, for example, three Cartesian coordinates of a particular point on the tip and three angles indicating tip pitch, roll and yaw. It has an arrangement that can be defined. The velocity associated with the change in placement coordinates over time can be measured directly or can be calculated using measurements at different times. Given the joint position and velocity θ and dθ / dt and the kinematic deductive knowledge of the instrument 610, the Cartesian position, orientation, translational velocity, and angular velocity of the tip relative to the instrument 610 coordinate system are calculated. Both forward kinematic models and differential kinematic models can be created. Forward kinematic models and differential kinematic models of kinematic chains can be easily constructed according to known methods. For example, the procedure described in John J. Craig, “Introduction to Robotics: Mechanics and Control,” Pearson Education Ltd. (2004), incorporated herein by reference, may be used. Step 715 determines the desired tip position, orientation, translational velocity, and angular velocity, which can be performed in the manner described above.

  In other embodiments, a sensor, such as a shape sensor, is described in Giuseppe M., which is incorporated herein by reference. It can be used to directly measure the position and orientation of Cartesian coordinates, as described in US Patent Application Publication No. 20090324161, named “Fiber optical shape sensor” by Prisco. The translational velocity associated with the change in placement coordinates over time can be calculated using measurements at different times. Unlike translational velocity, angular velocity cannot simply be calculated by a differential approach due to the amount of angular nature. However, methods for calculating angular velocities associated with orientation changes are known in the art, see, for example, L.A. Sciavico and B.M. "Modelling and Control of Robot Manipulators," Springer 2000, pp. 109-111.

Process 700B calculates a tip error at step 722. In one embodiment, step 722 includes a positional error or difference e _POS between the desired Cartesian coordinate of the tip and the current Cartesian coordinate of the tip, the desired translation speed of the tip, and the current translation of the tip. Translational velocity error or difference e _VT between velocity, orientation error or difference e _ORI between the desired orientation coordinate of the tip and the current orientation coordinate of the tip, and the desired angular velocity of the tip Calculating an angular velocity error or difference e _VA between the current angular velocity of the tip. Unlike the position error e _POS , the orientation error e _ORI cannot simply be calculated by the differential approach due to the amount of angular nature. However, methods for calculating the change in orientation are known in the art, see for example L.A. Sciavico and B.M. "Modelling and Control of Robot Manipulators," Springer 2000, pp. 109-111.

At step 724, process 700B determines a tip force F _TIP and tip torque τ _TIP that are intended to move the tip from the current configuration to the desired configuration. In this embodiment of the invention, the tip force F _TIP is determined by the errors e _POS and e _VT . For example, the angular component F _X , F _Y , or F _Z of the tip force F _TIP can be calculated using Equation 4, where gp _i and gv _i are gain factors and Cf _i is a constant. Tip torque tau _TIP can be determined in a similar manner, in this method, each component tau _i of the distal end portion torque, as shown in equation 5, another set Gori _i gain coefficients and constants , Gva _i , and Cτ _i are functions of error e _ORI and e _VA . In general, the gain factors gp _i and gv _i associated with different force or torque components F _i and τ _i may be different. Having different gain factors and constants for each component of tip force F _TIP and tip torque τ _TIP provides flexibility to identify the dynamic behavior of the end effector or instrument tip and is more effective Increase the interaction of the instrument with the tissue. For example, when guiding the instrument into a small lumen, a high value can be set for the gain factor along the insertion direction, while a low value can be set for the gain factor of the tip force orthogonal to the insertion direction. Thereby, the instrument has a low lateral resistance to the tissue while being stiff enough for insertion to prevent damage to the surrounding tissue. In another example, when using an instrument to drill a hole in tissue in a certain direction, increasing the gain coefficient of the tip torque and the gain coefficient along the insertion direction of the tip force can increase the drilling operation. make it easier.
Formula 4: F _i = gp _i * e _POS + gv _i * e _VT + Cf _i
Formula 5: τ _i = gori _i * e _ORI + gva _i * e _VA + Cτ _i
Step 732 determines a set of joint torques that provides the tip force F _TIP and tip torque τ _TIP determined in step 724. The relationship between the joint torque vector τ, the tip force F _TIP and the tip torque τ _TIP is well documented and is usually described as Equation 6, where J ^T is the kinematic chain of the instrument This is the transposed matrix of the well-known Jacobian matrix J.

Equation 6

ヤコビ行列Ｊは、器具の幾何学的形状及びステップ７１０で決定された現在のジョイント位置によって決まり、既知の方法を使用して作ることができる。例えば、参照により本願に援用される、Ｊｏｈｎ Ｊ． Ｃｒａｉｇ， "Ｉｎｔｒｏｄｕｃｔｉｏｎ ｔｏ Ｒｏｂｏｔｉｃｓ： Ｍｅｃｈａｎｉｃｓ ａｎｄ Ｃｏｎｔｒｏｌ，" Ｐｅａｒｓｏｎ Ｅｄｕｃａｔｉｏｎ Ｌｔｄ．(２００４)は、ロボット機構のためのヤコビ行列を作るために使用され得る技法を記載する。幾つかの場合、医療器具に提供された余分な又は冗長な動きの自由度の、例えば、６自由度より大きい先端部の動き、がある場合、先端部力Ｆ_ＴＩＰ及び先端部トルクτ_ＴＩＰを提供するジョイントトルクのセットは一意的ではなく、制約条件が、所望の特性を有するジョイントトルクのセットを選択するために、例えば、ジョイントが動きの範囲又は支持荷重におけるそれらの機械的なジョイントの限界に達することを防ぐジョイントトルクのセットを選択するために、或いは操作中に器具の任意の特定のジョイントに余分な用役を実行させるために、使用され得る。例えば、中央範囲のジョイント位置からの、ヤコビ行列の転置行列Ｊ^Ｔに関連するゼロ空間からの偏差を最小にする、ジョイントトルクのセットを選択することによってジョイントがそれらの機械的なジョイントの限界に達することを防ぐことができる。ジョイントトルクのセットは、式７にしたがって選択され得る。式７では、Ｐ（θ）は解によって提供されることになる追加有用性を定めるポテンシャル関数であり、∇は勾配演算子、Ｎ（）は、入力に関連したヤコビ行列の転置行列Ｊ^Ｔのゼロ空間からジョイントトルクのセットを選択するゼロ空間射影演算子である。１つの実施形態では、ポテンシャルＰ（θ）は、ジョイントがそれらの動きの範囲の中心にある場合に最小値を有するジョイント位置の２次関数である。ポテンシャル関数の勾配−∇Ｐ（θ）は、動きの範囲の中心に向かって動くようにジョイントを引くジョイントトルクのセットを選択する一方、ゼロ空間射影演算子Ｎ（）は、所望の先端部力及び先端部トルクを提供する選択されたジョイントトルクのセットもまた追加的な有用性を満足することを強制する。冗長な動きの自由度を提供するロボットシステムにおいて制約条件を使用するための技法は、技術分野で知られているとともに、ロボット工学の文献に見つけることができる。例えば、Ｙｏｓｈｉｈｉｋｏ Ｎａｋａｍｕｒａ， "Ａｄｖａｎｃｅｄ Ｒｏｂｏｔｉｃｓ: Ｒｅｄｕｎｄａｎｃｙ ａｎｄ Ｏｐｔｉｍｉｚａｔｉｏｎ，" Ａｄｄｉｓｏｎ−Ｗｅｓｌｅｙ (１９９１)、及びＯｕｓｓａｍａ Ｋｈａｔｉｂ，による文献“Ｔｈｅ Ｏｐｅｒａｔｉｏｎａｌ Ｓｐａｃｅ Ｆｒａｍｅｗｏｒｋ，" ＪＳＭＥ Ｉｎｔｅｒｎａｔｉｏｎａｌ Ｊｏｕｒｎａｌ， Ｖｏｌ． ３６， Ｎｏ． ３， １９９３を参照。

式７

The Jacobian matrix J depends on the instrument geometry and the current joint position determined in step 710 and can be made using known methods. See, for example, John J., incorporated herein by reference. Craig, "Introduction to Robotics: Mechanics and Control," Pearson Education Ltd. (2004) describes a technique that can be used to create a Jacobian matrix for a robotic mechanism. In some cases, if there is an extra or redundant movement freedom provided to the medical device, for example, tip movement greater than 6 degrees of freedom, the tip force F _TIP and tip torque τ _TIP are The set of joint torques provided is not unique and the constraints are limited to those mechanical joints in the range of motion or support load, for example, in order to select a set of joint torques with the desired characteristics. Can be used to select a set of joint torques that prevent reaching or to allow any particular joint of the instrument to perform extra utility during operation. For example, by selecting a set of joint torques that minimizes the deviation from the zero space associated with the Jacobian transpose matrix J ^T from the joint range of the central range, the joints are at the limit of their mechanical joints. Can be prevented from reaching. The set of joint torques can be selected according to Equation 7. In Equation 7, P (θ) is a potential function that defines the additional utility that will be provided by the solution, ∇ is the gradient operator, and N () is the Jacobian transpose matrix J ^T associated with the input. A zero space projection operator that selects a set of joint torques from zero space. In one embodiment, the potential P (θ) is a quadratic function of the joint position that has a minimum value when the joint is at the center of their range of motion. The gradient of the potential function -∇P (θ) selects a set of joint torques that pulls the joint to move toward the center of the range of motion, while the zero space projection operator N () determines the desired tip force. And a set of selected joint torques that provide tip torque also enforces additional utility. Techniques for using constraints in robotic systems that provide redundant motion freedom are known in the art and can be found in the robotics literature. For example, Yoshihiko Nakamura, “Advanced Robotics: Redundancy and Optimization,” Addison-Wesley (1991), and Osama Khatib, “The OperationalSmeSw. 36, no. 3, 1993.

Equation 7

ステップ７３２の後、プロセス７００Ｂは、上述のプロセス７００と同じ方法で継続する。特に、ステップ７３２で決定されたジョイントトルクに基づいて、ステップ７３５は張力Ｔ_ＤＩＳＴを決定する。ステップ７４０及び７４５は張力Ｔ_ＤＩＳＴへの修正値Ｔ_ＰＲＯＸ及びＴ_ＰＡＩＲを決定し、ステップ７５０は組合せ張力ベクトルＴを決定する。ステップ７５５及び７６０は、次に医療器具を時間間隔Δｔの間駆動するために、伝達システムに組合せ張力ベクトルＴの成分を加えるとともに保持する。

After step 732, process 700B continues in the same manner as process 700 described above. In particular, based on the joint torque determined in step 732, step 735 determines the tension _TDIST . Steps 740 and 745 determine correction values T _PROX and T _PAIR to the tension T _DIST and step 750 determines the combined tension vector T. Steps 755 and 760 then add and hold a component of the combined tension vector T to the transmission system to drive the medical device for the time interval Δt.

  The processes 700 and 700B of FIGS. 7A and 7B require a tension determination that produces a specific set of joint torques. The tendon tension for a single joint can be determined from the joint torque by simply dividing the joint torque by the moment arm where the tension is applied. In the case of multi-joints, the problem would be to solve simultaneous equations with constraints due to the geometry of the transmission system and cable path and the redundancy of the drive cable. In one particular embodiment, when solving simultaneous equations, non-negative tendon tension constraints (or minimum tension constraints) may be applied to prevent loosening of other tendons in the cable or transmission system. The input in question is the determined joint torque for each joint, while the geometry of the cable path defines the simultaneous equations (or coupling matrix A in Equation 3). An appropriate tendon tension that satisfies Equation 3 and is greater than the minimum tension constraint is required. A standard optimization method, called the simplex method, can be used to handle this inverse matrix problem with inequalities and optimal constraints. The simplex method requires a relatively large computation time and may not be advantageous for use in real-time applications. Also, the simplex method does not guarantee solution continuity when the joint torque changes. To speed up computational efficiency and provide a continuous output solution, an iterative approach that depends on the triangular nature of the coupling matrix A can be considered. FIGS. 8A, 8B, 8C, 9A, 9B, 9C, 9D, and 9E show some specific examples of joints in a multi-joint instrument, where some properties of the coupling matrix A of Equation 3 are illustrated. Used for.

  FIG. 8A shows a portion of an instrument that includes, for example, a plurality of mechanical joints 810, 820, and 830. Each joint 810, 820, and 830 provides one degree of freedom corresponding to rotation about the joint axis z1, z2, or z3. In FIG. 8A, tendons C 1 and C 2 connect to joint 810 for driving joint 810. The tendons C3 and C4 pass through the joint 810 and connect to the joint 820 for driving the joint 820. Tendons C5 and C6 penetrate joints 810 and 820 and connect to joint 830 for driving joint 830. The proximal ends (not shown) of tendons C1-C6 can be connected to respective drive motors or actuators through a compliant transmission system as shown in FIG. 2 or 3A. A control system for the instrument controls the actuator to apply respective tensions T1, T2, T3, T4, T5, and T6 to tendons C1, C2, C3, C4, C5, and C6.

The joint 830 is at the distal end of the illustrated embodiment of the instrument, and the driving of the joint 830 is controlled using a single joint process as described above with reference to FIGS. 5A, 5B, 5C, and 5D. Can be done. However, the total torque of the joint 820 is determined not only by the tension of the cables C3 and C4, but also by the torque applied by tendons C5 and C6 connected to the joint 830. The total torque of joint 810 is similarly determined not only by the tension of tendons C1 and C2, but also by the torque applied by tendons C3, C4, C5, and C6 connected to joints 820 and 830 near the distal end. A model based on the geometric or kinematic nature of the instrument will associate the torques τ1, τ2, and τ3 of the joints 810, 820, and 830 with the tendon tensions T1, T2, T3, T4, T5, and T6. Can be made. Equation 3A shows one such mathematical model and provides a specific example of Equation 3 above. In Equation 3A, τ ₁ , τ ₂ , and τ ₃ are the drive torques of joints 810, 820, and 830, respectively, and r ₁ , r ₂ , and r ₃ are accompanied by tendons C1, C3, and C5. The effective moment arm at the point T1, T2, T3, T4, T5, and T6 are the tensions at the respective tendons C1, C2, C3, C4, C5, and C6. The model that yields Equation 3A is that the axes of rotation z1, z2, or z3 are parallel and in the same plane, and tendons C1 and C2, C3 and C4, C5 and C6 are effective moment arms r1, r2, or r3, respectively. With joints 810, 820, and 830, the tendons C1, C3, and C5 include manipulating the respective joints 810, 820, and 830 in the opposite direction of rotation of the tendons C2, C4, and C6, respectively. Apply a specific set of geometric or mechanical properties of the instrument.

Formula 3A

図８Ｂ及びｂＣは、互いに直交するそれぞれの回転軸ｚ１及びｚ２を持つジョイント８１０及び８２０を含む医療器具の特性を示す。一般的に、各ジョイント８１０及び８２０における正味のトルクは、ジョイントを通って遠位端部に延びるテンドンの張力及びジョイントの駆動軸に対するテンドンに関連する有効モーメントアームによって決まる。図８Ｃは、各テンドンＣ１、Ｃ２、Ｃ３、及びＣ４が軸ｚ１及びｚ２周りの異なるモーメントアームで動作する典型的な例を示すために、ジョイント８１０の基部の図を示す。ジョイント８１０及び８２０を孤立系又は器具の遠位端部の最後の２つの作動するジョイントとして考えると、ジョイント８１０及び８２０の正味のトルクτ_１及びτ_２は、式３Ｂに示されるように、それぞれのテンドンＣ１、Ｃ２、Ｃ３、及びＣ４の張力Ｔ１、Ｔ２、Ｔ３、及びＴ４に関連する。特に、ジョイント８２０は、テンドンＣ３の張力Ｔ３及びテンドンＣ３がジョイント８２０に付く軸ｚ２に関するモーメントアームａ３２、並びにテンドンＣ４の張力Ｔ４及びテンドンＣ４がジョイント８２０に付く軸ｚ２に関するモーメントアームａ４２によって決まる正味のトルクτ_２にさらされる。ジョイント８１０のトルクτ_１は、ジョイント８１０に取付けられるテンドンＣ１及びＣ２の張力Ｔ１及びＴ２、ジョイント８２０に取付けられるテンドンＣ３及びＣ４の張力Ｔ３及びＴ４、並びにモーメントアームａ１１、ａ２１、ａ３１、及びａ４１によって決まる。モーメントアームａ２１及びａ４１は、引っ張りテンドンＣ２及びＣ４がジョイント８１０のトルクτ_１のための慣例定義の正の方向の反対の方向への回転を作り出すため、負符号が与えられる。同じ理由で、モーメントアームａ３１もまた、引っ張りテンドンＣ３がジョイント８２０の正の回転の方向と反対の回転を作り出すので、負符号が与えられる。

式３Ｂ

FIGS. 8B and bC illustrate the characteristics of a medical device that includes joints 810 and 820 having respective rotation axes z1 and z2 that are orthogonal to each other. In general, the net torque at each joint 810 and 820 is determined by the tension of the tendon that extends through the joint to the distal end and the effective moment arm associated with the tendon relative to the drive shaft of the joint. FIG. 8C shows a base view of joint 810 to show a typical example where each tendon C1, C2, C3, and C4 operates with different moment arms about axes z1 and z2. Considering joints 810 and 820 as isolated systems or the last two actuating joints at the distal end of the instrument, the net torques τ ₁ and τ ₂ of joints 810 and 820, respectively, as shown in Equation 3B, respectively: Related to the tensions T1, T2, T3, and T4 of the tendons C1, C2, C3, and C4. In particular, the joint 820 has a net tension determined by the tension T3 of the tendon C3 and the moment arm a32 with respect to the axis z2 where the tendon C3 is attached to the joint 820, and the moment arm a42 with respect to the axis z2 where the tension T4 of the tendon C4 and tendon C4 is attached to the joint 820. Exposed to torque τ ₂ . The torque τ ₁ of the joint 810 is caused by the tensions T1 and T2 of tendons C1 and C2 attached to the joint 810, the tensions T3 and T4 of tendons C3 and C4 attached to the joint 820, and moment arms a11, a21, a31, and a41. Determined. Moment arms a21 and a41 are given a negative sign because tensile tendons C2 and C4 create a rotation in the opposite direction of the conventional positive definition for torque τ ₁ of joint 810. For the same reason, the moment arm a31 is also given a negative sign because the tension tendon C3 creates a rotation opposite to the direction of the positive rotation of the joint 820.

Formula 3B

式３の行列Ａを計算するための同様の方法が、ジョイント軸が互いに平行又は直行せず、むしろ任意の相対的な向きであるとき、それに応じて各ジョイント軸に関する各テンドンのモーメントアームを計算することによって、利用され得ることが理解されるべきである。

A similar method for calculating the matrix A of Equation 3 calculates the moment arm of each tendon for each joint axis accordingly when the joint axes are not parallel or orthogonal to each other, but rather in any relative orientation. It should be understood that it can be utilized by doing so.

FIG. 9 is commonly found in medical catheters, gastrointestinal tract, colon, and bronchial endoscopes, guide wires, and other endoscopic instruments such as grasping devices and needles used for tissue sampling. A portion 900 of an instrument including a continuous continuous flexible joint 910 is shown. Joint 910 is similar to the flexible structure described above with reference to FIG. 3B. However, joint 910 is manipulated through the use of three or more tendons 920 to provide a joint with two degrees of freedom of motion. For example, FIG. 9B shows a view of the base of an embodiment of four tendons 920, labeled c1, c2, c3, and c4 in FIG. 9B that connects to the ends of the flexible joint 910. The difference in tension at tendons c1 and c2 can cause joint 910 to rotate in a first direction, eg, about the X axis, and the difference in tension at tendons c3 and c4 causes joint 910 to be Rotation in a second direction orthogonal to the direction, for example, rotation about the Y axis can be generated. The net torque components τ _X and τ _Y that tend to bend the joint 910 are determined from the tensions T1, T2, T3, and T4 of tendons c1, c2, c3, and c4, respectively, as shown in Equation 3C. obtain. As can be seen from Equation 3C, the equations for torque components τ _X and τ _Y are not coupled in that component τ _X is determined solely by tensions T1 and T2, and component τ _Y is determined solely by tensions T3 and T4.

Formula 3C

図９Ｃは、ジョイント９１０を駆動するために、図９Ｃにｃ１、ｃ２、及びｃ３で標識される、３つのテンドン９２０を使用する実施形態の基部の図を示す。この配置を用いて、ジョイント９１０を曲げる傾向がある正味のトルクの成分τ_Ｘ及びτ_Ｙは、式３Ｄに示されるように、テンドンｃ１、ｃ２、及びｃ３の張力Ｔ１、Ｔ２、及びＴ３それぞれから決定され得る。ここで、ｒａはＸ軸周りのテンドンｃ１のモーメントアームであり、−ｒｂはＸ軸周りのテンドンｃ２及びｃ３のモーメントアームであり、ｒｃ及び−ｒｃはそれぞれＹ軸周りのテンドンｃ２及びｃ３のモーメントアームである。Ｘ軸周りのテンドンｃ２及びｃ３のモーメントアームは、引っ張りテンドンｃ２及びｃ３が、引っ張りテンドンｃ１がジョイント９１０をＸ軸周りに曲げる方向と反対の方向に、ジョイント９１０を曲げるため、慣例により負符号が与えられる。同じ理由で、Ｙ軸周りのテンドンｃ３のモーメントアームは慣例により負符号が与えられる。

式３Ｄ

FIG. 9C shows a base view of an embodiment that uses three tendons 920, labeled c1, c2, and c3 in FIG. 9C to drive the joint 910. FIG. Using this arrangement, the net torque components τ _X and τ _Y that tend to bend the joint 910 are derived from the tensions T1, T2, and T3 of tendons c1, c2, and c3, respectively, as shown in Equation 3D. Can be determined. Here, ra is a moment arm of tendon c1 around the X axis, -rb is a moment arm of tendons c2 and c3 around the X axis, and rc and -rc are moments of tendons c2 and c3 around the Y axis, respectively. It is an arm. The moment arms of tendons c2 and c3 about the X axis have a negative sign by convention because the tension tendons c2 and c3 bend the joint 910 in a direction opposite to the direction in which the tension tendon c1 bends the joint 910 around the X axis. Given. For the same reason, the tendon c3 moment arm around the Y axis is conventionally given a negative sign.

Formula 3D

図９Ｄは、柔軟な器具９５０、例えば柔軟なカテーテルが２つのジョイントを含む実施形態を示す。ジョイント９１０は、２自由度の動きを提供するようにテンドン９２０を通じて駆動され、ジョイント９４０は、別の２自由度の動きを提供するようにテンドン９３０を通じて駆動される。図９Ｅは、ジョイント９１０のために３つのテンドン９２０（図９Ｅにおいてｃ１、ｃ２、及びｃ３で標識される）及びジョイント９４０のために３つのテンドン９３０（図９Ｅにおいてｃ４、ｃ５、及びｃ６で標識される）を使用する特定の場合におけるジョイント９４０の基部を示す。最遠位ジョイント９１０におけるトルクと力の間の関係は、上述の式３Ｄを使用してモデル化され得る。しかし、ジョイント９４０におけるトルクは、柔軟な部分９４０を通過するテンドン９２０及び９３０の全ての張力によって決まる。したがって、器具９５０のトルク及び張力は、式３Ｅに示されるような１つの特定の例に関係し得る。式３Ｅにおいて、τ１_Ｘ及びτ１_Ｙはジョイント９１０におけるトルク成分であり、τ２_Ｘ及びτ２_Ｙはジョイント９４０におけるトルク成分であり、ｒａ、ｒｂ、及びｒｃはモーメントアームの大きさであり、Ｔ１，Ｔ２、及びＴ３はテンドン９２０における張力であり、Ｔ４，Ｔ５、及びＴ６はテンドン９３０における張力である。

式３Ｅ

FIG. 9D shows an embodiment in which a flexible instrument 950, eg, a flexible catheter, includes two joints. Joint 910 is driven through tendon 920 to provide two degrees of freedom movement, and joint 940 is driven through tendon 930 to provide another two degrees of freedom movement. FIG. 9E shows three tendons 920 (labeled c1, c2, and c3 in FIG. 9E) for joint 910 and three tendons 930 (labeled c4, c5, and c6 in FIG. 9E) for joint 940. The base of the joint 940 in a particular case using The relationship between torque and force at the most distal joint 910 can be modeled using Equation 3D above. However, the torque at joint 940 is determined by the total tension of tendons 920 and 930 passing through flexible portion 940. Thus, the torque and tension of the instrument 950 may relate to one particular example as shown in Equation 3E. In Equation 3E, τ1 _X and τ1 _Y are torque components at joint 910, τ2 _X and τ2 _Y are torque components at joint 940, ra, rb, and rc are moment arm sizes, and T1, T2 , And T3 are tensions in tendon 920, and T4, T5, and T6 are tensions in tendon 930.

Formula 3E

式３Ａ乃至３Ｅは、多くの医療器具において、最遠位ジョイントにおいて特定のトルクを提供する張力を見つける問題が系における他の張力と独立して解かれ得ることを示す。より一般的には、各ジョイントのためのジョイントトルクは、そのジョイントに接続するテンドンにおける張力及び最遠位ジョイントに加えられる張力によって決まる。したがって、図７Ａ及び７Ｂのプロセス７００及び７００Ｂのステップ７３５は、あるジョイントトルクのセットを作り出す張力のセットを決定するために、器具の遠位端部から器具の近位端部に向かって順番にジョイントを反復的に解析するプロセスを使用して実行され得る。

Equations 3A through 3E show that in many medical devices, the problem of finding a tension that provides a specific torque at the distal most joint can be solved independently of other tensions in the system. More generally, the joint torque for each joint depends on the tension in the tendon connecting to that joint and the tension applied to the most distal joint. 7A and 7B, step 735 of FIGS. 7A and 7B, in turn, in order from the distal end of the instrument to the proximal end of the instrument to determine a set of tensions that produce a set of joint torques. It can be performed using a process of iteratively analyzing joints.

FIG. 10 shows an iterative process 735 for calculating the tension that creates a set of joint torques. Process 735 in the embodiment of FIG. 10 begins with a tension determination for the last or most distal joint, and then determines the tension for the joint in order toward the first or nearest joint. Step 1010 initializes the index j. This index j identifies the joint for analysis and is initially set to the number of joints L. Step 1020 then obtains the torque τ _j for the j th joint. The joint torque τ _j can be determined, for example, as in step 730 of process 700 or step 732 of process 700B described above, and one non-zero component or 2 for a joint that provides one degree of freedom motion. It can have two non-zero components for joints that provide freedom of movement.

  Step 1030 will then be applied to the jth joint through a link attached to the jth joint to create a net torque, eg, calculated in step 730 or 732 of FIG. 7A or 7B. Calculate tension. In the example of FIG. 10, the calculation of step 1030 is under the constraint that one of the directly applied tensions is the target or nominal tension. The nominal tension may be zero or alternatively the minimum tension that ensures that the tendon of the transmission system does not loosen so that the tension of the transmission system is released, but this is not essential. The nominal tension corresponds to when the actuator force is released, for example, when the drive motor 640 of FIG. 6 rotates freely, in which case the tension can depend on the type of transmission system used, Is not required.

  In the specific case where the jth joint of the medical device provides one degree of freedom movement and is directly coupled to two tendons or transmission systems, the joint torque is related to tension by one of the equations in Equation 3. Has one component. Step 1030 for the L th or most distal joint then involves solving a linear equation relating the joint torque to the two tensions associated with the distal most joint. Applying the constraint that one tension is the nominal tension to one linear equation involving two unknown tensions guarantees a unique solution for the other tension. In particular, another tension can be uniquely determined from the torque of the distal most joint and the associated coefficients of the coupling matrix A. Alternatively, if the L-th joint provides two degrees of freedom and is coupled to three tendons or transmission systems, the joint torque has two components and two from Equation 3 Corresponds to an expression. Since the two equations include three tensions, the remaining two tensions are uniquely determined from the joint torque component and the associated component of the coupling matrix A, with the constraint that one of the tensions is equal to the nominal tension. Can be done. The proposed method is similar, if m is greater than 3 and m tendons are connected to the same joint providing two degrees of freedom, then the (m-2) tension is simultaneously reduced to the nominal tension. It should be noted that while being constrained to be general, it is general in the sense that the remaining two tensions can be uniquely determined from the components of the joint torque and the associated components of the coupling matrix A.

  Step 1030 is first performed on the most distal joint (ie, j = L). Sub-step 1032 of step 1030 first selects one of the transmission systems attached to the most distal joint, and sub-step 1034 sets the tension to the nominal tension for sub-step 1036 calculations. Substep 1036 first calculates the tension (or tensions) for other transmission systems attached to the joint, and the calculated tension is applied directly to the calculated joint torque and the distal-most joint. Only depends on other tensions. Step 1038 determines whether all calculated tensions are greater than or equal to the minimum allowable tension. Otherwise, step 1040 selects another transmission system that is directly coupled to the joint so that if steps 1034 and 1036 are repeated, the transmission system has a nominal tension. Once step 1040 determines that all the calculated tensions are greater than or equal to the minimum allowable tension, the tension determination for the distal-most joint is complete and step 1050 is step 1060 for process 735 to repeat step 1020. Before returning from and branching, the joint index j is decremented.

  Step 1030 for the j-th joint in the case of a joint where two transmission systems are connected and provide one degree of freedom motion involves evaluation of one expression out of Equation 3 (determining a numerical value). . As described above, the nature of the coupling matrix A is that the formula for the jth joint includes only the tension associated directly with the Jth joint and the tension associated with the more distal joint. Thus, if the tension for the more distal joint has already been determined, the equation associated with the jth joint contains only two unknowns, which are the transmission system directly coupled to the joint. Tension. The constraint that one of the tensions is the nominal tension allows a unique determination of another tension that is above the nominal tension. If the j-th joint connects to three transmission systems and provides two degrees of freedom movement, it involves evaluation of two equations related to the two components of the joint torque. If the tension for the more distal joint has already been determined, the equation associated with the jth joint contains only three unknowns, which are the tensions of tendons directly coupled to the joint . The constraint that one of the tensions is the nominal tension allows a unique determination of the remaining two tensions that are above the nominal tension.

  The process 735 of FIG. 10 thus provides the complete distal tension set output at step 1070 when step 1060 determines that the most distal joint is being evaluated. A forward tension determination from the end joint may be used. Process 735 uses a computer or other computer system that operates for real-time determination of tension that is changed at a rate that provides sufficiently smooth movement to the medical procedure, for example, up to 250 Hz or greater. And can be implemented efficiently. Furthermore, the constraint that each joint has a tension applied directly at at least one target or nominal value provides continuity between tensions determined in continuous time.

  The process described above can be implemented or controlled using software that can be stored on a computer-readable medium, such as an electronic memory or magnetic or optical disk for execution by a general purpose computer. Alternatively, the control of the process described above or the calculations used in the process described above may be implemented using application specific hardware or electronics.

  Although the invention has been described with reference to particular embodiments, the description is only an example of the invention's application and should not be taken as a limitation. Various adaptations and combinations of features of the embodiments disclosed are within the scope of the invention as defined by the following claims.

Claims (42)

A medical device system:
With multiple joints;
With multiple actuators;
A plurality of transmission systems each having a proximal end coupled to the actuator, wherein each of the transmission systems is configured to allow transmission of force for a joint of the medical device system; A plurality of transmission systems having a distal end attached to one of said joints;
A sensor coupled to measure the placement of the medical device;
A control system coupled to receive a configuration measurement, wherein the control system uses the configuration measurement to determine a tension for the transmission system and creates the tension in the transmission system Operating the actuator as described above, and a control system;
Medical instrument system. Each of the transmission systems is compliant and extends by an amount corresponding to more than the allowed inaccuracy at the joint joint under an adjusted value of actuator force.
The system of claim 1. The control system controls the tension applied to the transmission system so that it is independent of the position of the actuator;
The system of claim 1. The control system controls the tension applied to the transmission system so that it is independent of compliance of the transmission system or the joint;
The system of claim 1. The control system controls the tension applied to the transmission system so that it is independent of the length of the transmission system from the proximal end to the distal end;
The system of claim 1. The control system controls the tension applied to the transmission system so that it is independent of the shape of the transmission system from the proximal end to the distal end;
The system of claim 1. The control system is:
Determining a difference between a desired placement of the joint and a current placement of the joint;
Determining, from the difference, a joint torque that operates the joint to reduce the difference; and determining the tension that generates the joint torque;
Determining the tension using a process,
The system of claim 1. The control system is:
Determining a first difference between one current arrangement of the selected joint and a desired arrangement of the selected joint; and a first of the first difference and a first gain factor Using a product to determine a joint torque to actuate the selected joint;
Using the placement measurement in a process comprising:
The system of claim 1. The process by which the control system uses the configuration measurements is:
Determining a second difference between a current velocity at the selected joint and a desired velocity at the joint; and determining a second product of the second difference and a second gain factor. The joint torque for operating the selected joint is further determined by the second product;
Further having
The system according to claim 8. The control system is:
Determining a difference between a desired placement of the tip of the instrument and a current placement of the tip;
Determining from the difference a tip force and tip torque that reduces the difference when applied to the tip;
Determining a joint torque that generates the tip force and the tip torque at the tip of the instrument; and determining the tension that generates the joint torque;
Using the process to determine the tension,
The system of claim 1. The step of determining the tip force is:
Determining a first difference between a current value of the first position coordinate of the tip and a desired value of the first position coordinate of the tip;
Determining a first product of the first difference and a first gain factor; and using the first product to determine a first component of the tip force;
Having
The system according to claim 10. Determining the tip force comprises:
Determining a second difference between a current value of the second position coordinate of the tip and a desired value of the second position coordinate of the tip;
Determining a second product of the second difference and a second gain factor, the second gain factor being different from the first gain factor; and a second force of the tip force Using the second product to determine a component;
Further having
The system of claim 11. The step of determining the tip torque includes:
Determining a first difference between a current value of the first angular coordinate of the tip and a desired value of the first angular coordinate of the tip;
Determining a first product of the first difference and a first gain factor; and using the first product to determine a first component of the tip torque;
Having
The system according to claim 10. The step of determining the tip torque includes:
Determining a second difference between a current value of the second angular coordinate of the tip and a desired value of the second angular coordinate of the tip; and the second difference and a second gain. Determining a second product of coefficients, wherein the second gain coefficient is set to be different from the first gain coefficient;

Further having
The system of claim 13. The step of determining the tip force is:
Determining a difference between a current velocity component of the tip and a desired velocity component of the tip;
Determining a product of the difference and a gain factor; and using the product to determine a component of the tip force;
Having
The system according to claim 10. The step of determining the tip force is:
Determining a difference between an angular velocity of the tip and a desired angular velocity of the tip;
Determining a product of the difference and a gain factor; and using the product to determine a component of the tip force;
Having
The system according to claim 10. The joint provides more than six degrees of freedom of movement and includes a degree of freedom of movement that is redundant with respect to the movement of the tip, so that the joint torque keeps the joint from approaching the limits of the range of movement of the joint. Or calculated so as not to approach the joint torque limit,
The system according to claim 10. The control system is:
Using the placement measurements to determine a joint torque at each of the joints; and determining the tension for the transmission system using the joint torques;
Determining the tension using a process comprising:
The system of claim 1. The control system is:
Sequentially evaluating the joints from the distal end of the instrument to the proximal end of the instrument, wherein the step of evaluating each joint includes the joint for the joint Using torque and tension determined for the joint closer to the distal end of the instrument to determine the tension applied directly to the joint being evaluated,
Determining the tension using a process comprising:
The system of claim 18. When evaluating each joint, the tension of the transmission system applied directly to the joint being evaluated is chosen to be equal to the nominal value, and the tension of the remaining transmission system applied directly to the joint is Calculated to produce the joint torque for the joint and to be verified to be above the nominal value,
The system of claim 19. The nominal value is chosen to effectively release all tension in the transmission system,
The system according to claim 20. The nominal value is chosen to effectively hold the tension in the transmission system,
The system according to claim 20. The steps of determining the tension using the joint torque include:
Determining a distal tension from the joint torque; and determining a correction value depending on a respective difference between the speed of the joint and the corresponding speed of the actuator coupled to the joint, The tension for the transmission system depends on the distal tension and the correction value;
Having
The system of claim 18. The steps of determining the tension using the joint torque include:
Determining a distal tension from the joint torque; and determining a correction value for each of the joints that depends on a difference between the speeds of actuators coupled to the transmission system coupled to the joints; The tension for the transmission system depends on the distal tension and the correction value;
Having
The system of claim 18. A method for controlling a medical device comprising:
Measuring the placement of a plurality of joints of the medical device;
Receiving a command indicating a desired placement of the medical device;
Determining a tension for each of a plurality of transmission systems each connecting a plurality of actuators to the joint, wherein the determination of the tension is independent of the position of the actuators; and Operating the actuator to add;
Having
Method. One or more of the transmission systems have compliance so that they do not provide a relationship between the position of the joint and the position of the actuator coupled to the transmission system, the transmission system using the relationship Accurate enough to control the joints,
26. The method of claim 25. The steps for determining the tension are:
Determining a difference between a desired placement of the joint and a current placement of the joint;
Determining, from the difference, a joint torque that operates the joint to reduce the difference; and determining the tension that generates the joint torque;
Having
26. The method of claim 25. The steps for determining the tension are:
Determining a difference between a desired placement of the tip of the instrument and a current placement of the tip;
Determining from the difference a tip force and tip torque that reduces the difference when applied to the tip;
Determining a joint torque that generates the tip force and the tip torque at the tip of the instrument; and determining the tension that generates the joint torque;
Having
26. The method of claim 25. The step of determining the tip force is:
Determining a first difference between a current value of the first position coordinate of the tip and a desired value of the first position coordinate of the tip;
Determining a first product of the first difference and a first gain factor; and using the first product to determine a first component of the tip force;
Having
30. The method of claim 28. Determining the tip force comprises:
Determining a second difference between a current value of the second position coordinate of the tip and a desired value of the second position coordinate of the tip;
Determining a second product of the second difference and a second gain factor, the second gain factor being different from the first gain factor; and a second force of the tip force Using the second product to determine a component;
Further having
30. The method of claim 29. The step of determining the tip torque includes:
Determining a first difference between a current value of the first angular coordinate of the tip and a desired value of the first angular coordinate of the tip;
Determining a first product of the first difference and a first gain factor; and using the first product to determine a first component of the tip torque;
Having
30. The method of claim 28. Determining the tip torque comprises:
Determining a second difference between a current value of the second angular coordinate of the tip and a desired value of the second angular coordinate of the tip; and the second difference and a second gain. Determining a second product of coefficients, wherein the second gain coefficient is set to be different from the first gain coefficient;

Further having
32. The method of claim 31. The step of determining the tip force is:
Determining a difference between a current velocity component of the tip and a desired velocity component of the tip;
Determining a product of the difference and a gain factor; and using the product to determine a component of the tip force;
Having
30. The method of claim 28. The step of determining the tip force is:
Determining a difference between an angular velocity of the tip and a desired angular velocity of the tip;
Determining a product of the difference and a gain factor; and using the product to determine a component of the tip force;
Having
30. The method of claim 28. The joint provides greater than 6 degrees of freedom of motion and includes a degree of freedom of motion that is redundant with respect to the motion of the tip, and the step of determining the joint torque is at the limit of the range of motion of the joint. Using the redundant degree of freedom of movement so as not to approach the joint torque limit
30. The method of claim 28. The determination of the tension is:
Using the placement measurements to determine a joint torque at each of the joints; and determining the tension for the transmission system using the joint torques;
Having
26. The method of claim 25. The steps for determining the tension are:
Sequentially evaluating the joints from the distal end of the instrument to the proximal end of the instrument, wherein the step of evaluating each joint includes the joint for the joint Using torque and tension determined for the joint closer to the distal end of the instrument to determine the tension applied directly to the joint being evaluated,
Further having
37. A method according to claim 36. When evaluating each joint, the tension of the transmission system applied directly to the joint being evaluated is chosen to be equal to the nominal value, and the tension of the remaining transmission system applied directly to the joint is Calculated to produce the joint torque for the joint and to be verified to be above the nominal value,
38. The method of claim 37. The nominal value is chosen to effectively release all tension in the transmission system,
40. The method of claim 38. The nominal value is chosen to effectively hold the tension in the transmission system,
40. The method of claim 38. The steps for determining the tension are:
Determining a distal tension from the joint torque; and determining a correction value depending on a respective difference between the speed of the joint and the corresponding speed of the actuator coupled to the joint, The tension for the transmission system depends on the distal tension and the correction value;
Having
37. A method according to claim 36. The steps of determining the tension using the joint torque include:
Determining a distal tension from the joint torque; and determining a correction value for each of the joints that depends on a difference between the speeds of actuators coupled to the transmission system coupled to the joints; The tension for the transmission system depends on the distal tension and the correction value;
Having
37. A method according to claim 36.

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